High efficiency wind turbine having increased laminar airflow

ABSTRACT

A wind turbine is provided with turbine blades mounted for axial rotation about an axis. The blades are surrounded by a shroud to define an axial air passage. A conical ring is attached to the shroud and includes vanes for directing the airflow. Plates are attached to the shroud at a position radially outward from the shroud forming an air passage between the shroud and the plates. The plates have gaps between the adjacent plates so that air exiting the downstream opening of the shroud and air moving through the axial air passage between the shroud and the plates are mixed and a portion of the mixed air exits through the gaps.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation-in-Part of a pending U.S.patent application Ser. No. 13/094,952, filed Apr. 27, 2011.

FIELD OF THE INVENTION

The present invention relates to wind turbines. More particularly, thepresent invention relates to high efficiency wind turbines forextracting energy from the wind.

BACKGROUND OF THE INVENTION

Wind energy has been used for centuries for a variety of useful purposesincluding grinding grain and pumping water. Recently, there has beenextensive research and development worldwide in technology to use windto generate electricity. Generating electricity from wind power does notresult in the emission of carbon dioxide, hydrocarbons, carbon monoxide,particulates or other harmful compounds. Wind energy is, therefore, anattractive alternative to at least a portion of the power generated byburning fossil fuels in conventional power plants. The use of windenergy also reduces the need for coal mining which can be hazardous tominers and harmful to the environment.

There has been a continuing need and desire for improvements in winddriven power generators, including the desire to overcome theshortcomings of conventional power generators while also providing agenerator which is efficient and physically compact. This increasinglycompetitive source of energy is steadily providing a growing share ofworldwide electricity. Significant numbers of these wind turbines havebeen located in particular areas with high average wind speeds to formwind farms with considerable generating capability. Wind turbines havealso been used to generate electricity in off-grid applications such asremote sites.

Traditional wind turbines are typically mounted on tall towers. Thetowers are often placed in open fields or along a ridgeline. In,additionto accessing higher wind speeds, the height of traditional wind turbinesreduces or avoids risk to people, livestock, and wildlife that may be onor near the ground. But towers are expensive to build and, at least insome cases, their height may be objectionable, for example, forobstructing a view. Property owners in the vicinity of these windturbines also have been known to object to the noise caused by the largerotating blades. Many of these traditional wind turbines have bladesover 40 meters long, meaning the diameter of the rotor is over 80meters, mounted on towers 80 meters tall. Land for the wind farm has tobe purchased or leased, and transmission line easements have to beobtained from the wind farm to the existing transmission power grid. Asa result, the development time is long and costs are very high. Becauseof these restrictions, many new wind farms cannot be built for severalyears.

Thus, because of the problems associated with such traditional windfarms, much current research has been devoted to smaller wind turbines.While it is possible to create turbines with a wide range of bladelengths, much recent development has been devoted to turbines withsmaller blade lengths than those found in traditional wind turbines.These smaller turbines can be mounted on the roofs of buildings or onpoles, which are only a fraction of the height of traditional windturbine towers. However, typical small wind driven turbines arerelatively inefficient, often only converting a small fraction of thewind's kinetic energy into usable electrical power. When these smallerwind turbines have the blades mounted within a housing, or shroud, thedesigns allow for greater power extraction out of the wind, compared toprior art open designs. Examples of such wind turbines are found in U.S.Pat. Nos. 7,218,011, 4,204,799, 4,075,500, 6,655,907 and 6,887,031, thedisclosures of which are hereby incorporated by reference herein. Thesesmaller scale wind turbines may be mounted on lower poles, such as at aheight of 10 meters, or may be mounted on the top of buildings. Thus,the smaller turbines are less expensive to build, and create less of animpact on the environment compared to the traditional larger turbines. Asmall scale wind turbine is needed which is highly efficient and whichretains the other advantages of wind power generation.

BRIEF SUMMARY OF THE INVENTION

A wind turbine is provided for extracting energy out of an airflow. Thewind turbine includes a plurality of turbine blades mounted for rotationabout a longitudinal axis. For example, the blades could be mounted to arotating hub. In some embodiments, the turbine could have between 3 and20 blades. Preferably, the blades have a length which will extend almostall the way to the shroud which surrounds the blades. The shroud,preferably constructed from steel or aluminum, surrounds the turbineblades. The shroud could be cylindrical, conical, square or othersuitable shapes. The shroud has an upstream opening and a downstreamopening. A plurality of plates are attached to the shroud and can bespaced radially outward from the shroud or can be mounted on the surfaceof the shroud. The plates are constructed from any suitable materialsuch as steel, aluminum, or other materials known to those of skill inthe art. The plates could be attached at various positions along theaxis of the shroud, such as near the upstream opening, near thedownstream opening, or at a midpoint between the two. The plates arespaced around the circumference of the shroud and project beyond thedownstream opening of the shroud. The plates could be planar or arcuate,and could have a constant width, or a width which varies along thelongitudinal direction. The plates could have a curvature generallycorresponding to,the shroud. The plurality of plates form a seconddiscontinuous shroud. The shroud and the plurality of plates form asecond axial air passage between them. Because the plates form adiscontinuous shroud, there are gaps between adjacent plates such thatair exiting the downstream opening of the shroud and air moving throughthe axial air passage between the shroud and plates is mixed and aportion of the mixed air exits through the gaps. The ratio of the totalarea of the plates to the total area of the gaps is between 8:1 and 1:1,and is preferably 3:1. The plates can be tiled away from the axis ofrotation of the blades from 0 degrees to 40 degrees. The plates allowfor the wind turbine to turn about its mount so that the axis ofrotation is aligned with the wind direction. The gaps in the platescannot be so large as to prevent this alignment.

The wind turbine can also include a ring mounted near the downstreamopening of the plates and spaced radially outward from the plates tocreate a third axial air passage between the ring and the plates.

To further improve the efficiency of the turbine, a conical ring can beattached in the upstream opening of the shroud. The conical ring ispreferably made from steel, aluminum or other suitable material. Theconical ring has an upstream edge defining an upstream area, and adownstream edge defining a downstream area. The length of the conicalring may vary depending on the size of the shroud to which it isattached. The upstream area is larger than the downstream area. Thedegree of taper of the conical ring from the upstream edge to thedownstream edge and the thickness of the conical ring may vary, but theconical ring should be designed such that it does not introduceturbulence into the airflow. The conical ring causes increased airflowthrough the turbine by capturing more air and directing it through theturbine. The diameter of turbine blades defines a swept area. Thedownstream area of the conical ring is larger than the swept area of theblades. The conical ring includes a plurality of vanes between theupstream area and the downstream area. The vanes are generallyperpendicular to the swept area of the blades. The vanes reduceturbulence in the airflow and increase the energy transferred from theairflow to the turbine blades.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Embodiments and applications of the invention are illustrated by theattached non-limiting drawings. The attached drawings are for purposesof illustrating the concepts of the invention and may not be to scale.

FIG. 1 is a front elevation view of the a conical shroud and turbineblades in accordance with one embodiment of the present invention;

FIG. 2 is a side view of the shroud and turbine blades of FIG. 1;

FIG. 3 is a perspective view of the shroud and turbine blades of FIG. 1;

FIG. 4 is a front view of the shroud, turbine blades and plates inaccordance with one embodiment of the present invention;

FIG. 5 is a side view of the shroud, turbine blades and plates of FIG.4;

FIG. 6 is a perspective view of the shroud, turbine blades and plates ofFIG. 3;

FIG. 7 is a front elevation view of the a cylindrical shroud and turbineblades in accordance with another embodiment of the present invention;

FIG. 8 is a side view of the shroud and turbine blades of FIG. 7;

FIG. 9 is a perspective view of the shroud and turbine blades of FIG. 7;

FIG. 10 is a front view of the shroud, turbine blades and plates inaccordance with another embodiment of the present invention;

FIG. 11 is a side view of the shroud, turbine blades and plates of FIG.10;

FIG. 12 is a perspective view of the shroud, turbine blades and platesof FIG. 10;

FIG. 13 is a perspective view of another embodiment of the presentinvention;

FIG. 14 is a perspective view of another embodiment of the presentinvention;

FIG. 15 is a perspective view of another embodiment of the presentinvention;

FIG. 16 is a perspective view of a conical ring of the presentinvention;

FIG. 17 is a front elevation view of the conical ring of FIG. 16;

FIG. 18 is a perspective view of another embodiment of a conical ring ofthe present invention;

FIG. 19 is a front elevation view of the conical ring of FIG. 18;

FIG. 20 is a perspective view of another embodiment of the presentinvention; and

FIG. 21 is a perspective view of another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of the embodiments of the invention. Throughout thefollowing description, specific details are set forth in order toprovide a more thorough understanding of the invention. However, theinvention may be practiced without these particulars. In otherinstances, well known elements have not been shown or described indetail to avoid unnecessarily obscuring the disclosure. Accordingly, thespecification and drawings are to be regarded in an illustrative, ratherthan a restrictive, sense. FIGS. 1 through 21 show the variousembodiments of the invention. As best seen in FIGS. 1 through 3, thepresent invention includes a wind turbine 10 with a plurality of blades12 arranged around a hub 14. The blades 12 are capable of rotation aboutthe longitudinal axis 16. Surrounding the blades 12 is a shroud 20. Theshroud 20 is shown as conical in shape, but may be any one of manysuitable shapes. The conical shroud 20 includes an upstream opening 22and a downstream opening 24. A post 26 is provided to mount the windturbine 10 to a structure or above the ground. The conical shroud 20 hasfins 28 which assist in aligning the longitudinal axis 16 with thedirection of the wind 18.

Turning to FIGS. 4 through 6, plates 30 are mounted above the conicalshroud 20. The plates 30 have gaps 32 between them. The plates 30 aremounted on a mounting structure 34 such that they are mounted to thesurface of the conical shroud 20. The plates 30 project past thedownstream opening 24 (FIG. 2) of the conical shroud 20. As air movesthrough the upstream opening 22 of the conical shroud, past the blades12, it exits through the downstream opening 24 of the conical shroud 20.The function of blades 12 is accentuated by the downwind shroud 20 whichserves to reduce pressure which increases the velocity of the airdownwind of blades 12. A portion of the air exits through the gap 32.This configuration reduces the downstream air pressure and increases theefficiency of the wind turbine 10.

Optionally, an additional ring 40 is provided to create yet anothermoving airstream in the passage 42 between the plates 30 and the ring40. This air stream further reduces the pressure at the downstreamopening 24 (FIG. 2) of the conical shroud 20.

As shown in FIGS. 7 through 12, a cylindrical shroud 120 is shown, inplace of the conical shroud 20 (FIG. 3). The cylindrical shroud 120 hasfins 128 which assist in aligning the longitudinal axis 16 with thedirection of the wind 118. The plates 130 are shown as arcuate insteadof the planar plates 30 of FIG. 6. It will be understood by those ofskill in the art that various configurations of the plates 30 and 130can be used with the different embodiments of the invention disclosedherein. Turning to FIGS. 10-12, plates 130 are mounted above thecylindrical shroud 120. The plates 130 have fins 128 which assist inaligning the longitudinal axis 16 with the direction of the wind 118.The plates 130 have gaps 132 between them. The plates 130 are mounted ona mounting structure 134 such that they are raised off the surface ofthe cylindrical shroud 120. The plates 130 project past the downstreamopening 124 of the cylindrical shroud 120. As air moves through theupstream opening 122 of the shroud, past the blades 12, it exits throughthe downstream opening 124 of the cylindrical shroud 120. Air also movesin the passage 136 underneath the plates 130. The air moving through thepassage 136 mixes with the air exiting the downstream opening 124 (FIG.9) of the shroud 120. A portion of that air exits through the gap 132.This configuration reduces the downstream air pressure and increases theefficiency of the wind turbine 10.

Optionally, an additional ring 140 is provided to create yet anothermoving airstream in the gap 142 between the plates 130 and the ring 140.This third air stream further reduces the pressure at the downstreamopening 124 of the cylindrical shroud 120.

Turning to FIG. 13, a shroud 220 has curved plates 230 attached thereto.Fins 228 are between the curved plates 230. Between the plates 230 arealso gaps 232 near the downstream end 224 of the shroud 220. Between theshroud 220 and the curved plates 230 are passages 236. These passages236 are isolated from one another and from gaps 232. As air movesthrough the upstream opening 222 of the shroud 220, past the blades 12,it exits through the downstream opening 224 of the cylindrical shroud220. Air also moves in the passage 236 underneath the plates 230. Theair moving through the passage 236 mixes with the air exiting thedownstream opening 224 of the shroud 220. A portion of that air exitsthrough the gap 232. This configuration reduces the downstream airpressure and increases the efficiency of the wind turbine 10.

FIG. 14 shows another embodiment of the invention. A shroud 320 hasplates 330 attached to the surface 321 of the shroud 320. Fins 328 arebetween the plates 330. Optionally, a ring 340 is provided to create amoving airstream through gap 342 downwind of the opening 324. Thisairstream reduces the pressure at the downstream opening 324 of theshroud 320. Between the plates 330 are gaps 332 near the downstream end324 of the shroud 320. As air moves through the upstream opening 322 ofthe shroud 320, past the blades 12, it exits through the downstreamopening 324 of the cylindrical shroud 320. A portion of that air exitsthrough gaps 332, reducing the pressure at the downstream opening 324.

FIG. 15 shows another embodiment of the invention. A shroud 420 has fins428 spaced about the circumference. The fins 428, as described above,assist in aligning the shroud 420 with the airflow. Plates 430 aremounted on the shroud 420. Gaps 432 are provided between the plates 430to allow a portion of the airflow exiting past the blades 12 and thedownstream opening 424 to exit through the gaps 432 reducing thepressure at the downstream opening 424.

Another embodiment of the invention is shown in FIGS. 16-21. In FIGS. 16and 17, a conical ring 60 is shown with radial vanes 62 extending from ahub 64. The conical ring 60 captures airflow within the area defined byits upstream edge 66 and concentrates that airflow as it passes throughthe area defined by the downstream edge 68. As shown in FIG. 20, ashroud 520 surrounds the blades 12. The conical ring 60 is attached tothe shroud 520 by means known in the art such as screws, bolts, rivets,welding or other means. Fins 528 are between the curved plates 530.Between the plates 530 are also gaps 532 near the downstream end 524 ofthe shroud 520. Between the shroud 520 and the curved plates 530 arepassages 536. These passages 536 are isolated from one another and fromgaps 532. Air moves through the shroud 520, past the blades 12, and itexits through the downstream opening 524 of the shroud 520.

FIGS. 18 and 19 show another embodiment. The conical ring 160 has radialvanes 162 surrounding a hub 164. Circumferential vanes 170 are alsoprovided. The conical ring 160 captures airflow within the area definedby its upstream edge 166 and concentrates that airflow as it passesthrough the area defined by the downstream edge 168.

FIG. 21 shows the ring 60 attached to a shroud 620. The conical ring 160is attached to the shroud 620 by means known in the art such as screws,bolts, rivets, welding or other means. The blades 12 have a swept areawhich is inside of the edge 168. The vanes 162 make the air lessturbulent and provide for more efficient transfer of energy from the airto the blades 12. As with other embodiments, a shroud 620 surrounds theblades 12. Fins 628 are between the curved plates 630. Between theplates 630 are also gaps 632 near the downstream end 624 of the shroud620. Between the shroud 620 and the curved plates 630 are passages 636.These passages 636 are isolated from one another and from gaps 632. Airmoves through the shroud 620, past the blades 12, and it exits throughthe downstream opening 624 of the shroud 620.

The term “airflow” is used throughout this application to denote a fluidflow. Although the primary intent of invention is for the extraction ofenergy from wind, the principles and innovations may apply equally tothe flow of other fluids such as flowing water. It is to be understoodthat the exemplary embodiments are merely illustrative of the presentinvention and that many variations of the above-described embodimentscan be devised by one skilled in the art without departing from thescope of the invention.

The invention claimed is:
 1. A wind turbine for extracting energy out ofan airflow, the wind turbine having an axis of rotation, the windturbine comprising: turbine blades mounted for axial rotation and havinga swept area; a first shroud surrounding the turbine blades and defininga first axial air passage, the first shroud having an upstream openingand a downstream opening; a conical ring attached in the upstreamopening, the conical ring having an upstream edge defining an upstreamarea, and a downstream edge defining a downstream area, the upstreamarea being larger than the downstream area; a plurality of vanes betweenthe upstream area and the downstream area, the vanes generallyperpendicular to the swept area of the blades; a plurality of platesattached to the first shroud, the plates spaced radially outward fromthe first shroud, the plates spaced around the circumference of thefirst shroud and projecting beyond the downstream opening of the firstshroud, the plurality of plates forming a second discontinuous shroud;the first shroud and the plurality of plates forming a second axial airpassage between the first shroud and plurality of plates; the pluralityof plates having gaps between adjacent plates such that air exiting thedownstream opening of the first shroud and air moving through the secondaxial air passage are mixed and a portion of the mixed air exits throughthe gaps.
 2. The wind turbine of claim 1 wherein the ratio of the totalarea of the plates to the total area of the gaps is between 8:1 and 1:13. The wind turbine of claim 1 wherein the ratio of the total area ofthe plates to the total area of the gaps is approximately 3:1.
 4. Thewind turbine of claim 1 further including a ring mounted near thedownstream end of the plates and spaced radially outward from the platesto create a third axial air passage between the ring and the plates. 5.The wind turbine of claim 4 wherein the ring is continuous.
 6. The windturbine of claim 4 wherein the ring is discontinuous.
 7. The windturbine of claim 1 wherein the plates extend from a location near theupstream opening of the shroud to a location beyond the downstreamopening of the shroud.
 8. The wind turbine of claim 1 wherein the platesextend from a location near the midpoint between the upstream opening ofthe shroud and the downstream opening of the shroud to a location beyondthe downstream opening of the shroud.
 9. The wind turbine of claim 1wherein the plates are arcuate in shape.
 10. The wind turbine of claim 1wherein the plates have a curvature generally corresponding to theshroud.
 11. The wind turbine of claim 1 wherein the first shroud isconical.
 12. The wind turbine of claim 1 wherein the plates have a widthwhich increases in the direction of the airflow.
 13. The wind turbine ofclaim 1 wherein the number of blades is between 3 and
 20. 14. The windturbine of claim 1 wherein the vanes extend generally in the radialdirection.
 15. The wind turbine of claim 1 wherein the vanes extend inboth the radial and circumferential direction.
 16. A wind turbine forextracting energy out of an airflow, the wind turbine having an axis ofrotation, the wind turbine comprising: turbine blades mounted for axialrotation about a hub, the blades having a swept area; a firstcylindrical shroud surrounding the turbine blades and defining a firstaxial air passage, the first cylindrical shroud having an upstreamopening and a downstream opening; a conical ring attached in theupstream opening, the conical ring having an upstream edge defining anupstream area, and a downstream edge defining a downstream area, theupstream area being larger than the downstream area; a plurality ofvanes between the upstream area and the downstream area, the vanesgenerally perpendicular to the swept area of the blades; a plurality ofplates attached to the first cylindrical shroud, the plates spacedradially outward from the first cylindrical shroud, the plates spacedaround the circumference of the first cylindrical shroud and projectingbeyond the downstream opening of the first cylindrical shroud, theplurality of plates forming a second discontinuous shroud; the firstcylindrical shroud and the plurality of plates forming a second axialair passage between the first cylindrical shroud and plurality ofplates; the plurality of plates having gaps between adjacent plates suchthat air exiting the downstream opening of the first cylindrical shroudand air moving through the second axial air passage are mixed and aportion of the mixed air exits through the gaps.
 17. The wind turbine ofclaim 16 wherein the ratio of the total area of the plates to the totalarea of the gaps is between 8:1 and 1:1.
 18. The wind turbine of claim16 wherein the ratio of the total area of the plates to the total areaof the gaps is approximately 3:1.
 19. The wind turbine of claim 16further including a ring near the downstream end of the plates andspaced radially outward from the plates to create a third axial airpassage between the ring and the plates.
 20. The wind turbine of claim19 wherein the ring is continuous.
 21. The wind turbine of claim 19wherein the ring is discontinuous.
 22. The wind turbine of claim 16wherein the plates extend from a location near the upstream opening ofthe cylindrical shroud to a location beyond the downstream opening ofthe cylindrical shroud.
 23. The wind turbine of claim 16 wherein theplates extend from a location near the midpoint between the upstreamopening of the cylindrical shroud and the downstream opening of thecylindrical shroud to a location beyond the downstream opening of thecylindrical shroud.
 24. The wind turbine of claim 16 wherein the platesare arcuate in shape.
 25. The wind turbine of claim 16 wherein theplates have a curvature generally corresponding to the shroud.
 26. Thewind turbine of claim 16 wherein the plates have a width which increasesin the direction of the airflow.
 27. The wind turbine of claim 16wherein the number of blades is between 3 and
 20. 28. The wind turbineof claim 16 wherein the number of blades is
 6. 29. The wind turbine ofclaim 16 wherein the plates are angled away from the axis of rotation atan angle of between 0 degrees and 40 degrees.
 30. The wind turbine ofclaim 16 wherein the vanes extend generally in the radial direction. 31.The wind turbine of claim 16 wherein the vanes extend in both the radialand circumferential direction.
 32. A wind turbine for extracting energyout of an airflow, the wind turbine having an axis of rotation, the windturbine comprising: turbine blades mounted for axial rotation, theblades having a swept area; a first shroud surrounding the turbineblades and defining a first axial air passage, the first shroud havingan upstream opening and a downstream opening; a conical ring attached inthe upstream opening, the conical ring having an upstream edge definingan upstream area, and a downstream edge defining a downstream area, theupstream area being larger than the downstream area; a plurality ofvanes between the upstream area and the downstream area, the vanesgenerally perpendicular to the swept area of the blades; a plurality ofplates attached to the first shroud, the plates spaced around thecircumference of the first shroud and projecting beyond the downstreamopening of the first shroud, the plurality of plates forming a seconddiscontinuous shroud; the plurality of plates having gaps betweenadjacent plates such that a portion of the air exiting the downstreamopening of the first shroud exits through the gaps.
 33. The wind turbineof claim 32 wherein the vanes extend generally in the radial direction.34. The wind turbine of claim 32 wherein the vanes extend in both theradial and circumferential direction.